Of course I understand it loses value, my question is in your experience how much? Let’s say a signature baseball is worth 100$; it gets water damaged smudge a little. You drop your offer to $50, $60,$70 ect just asking for range and ideas of worth not quotes I know it’s very much situational

It's a case by case consideration. Depending on the rarity of the signature even the slightest damage, especially to the signature, can dramatically reduce the value. Actually, seeing the item in question would make it far easier to evaluate.

I agree that it’s on a very case-by-case basis hinging on value and supply.

For example, a Babe Ruth signed photo with some edge wearing and creases is not going to be affected much by minor condition issues. However, a Mickey Mantle signed photo with the slightest bit of damage will suffer a drastic reduction in value. The reason is that mint condition Mantle photos are in good supply. Why settle for a clunker when so many perfect ones exist?